Hydraulic actuator with internal dashpot



Dec. 31, 1968 J. H. MERCIER 3,418,888 HYDRAULIC ACTUATOR WITH INTERNAL DASHPOT Filed April 26, 1967 Sheet 1 of 2 INVENTOR dice ass 66 NEACIER ATTORNEY Dec. 31, 1968 J. H. MERCIER 3,418,888

HYDRAULIC ACTUATOR WITH INTERNAL DASHPOT Filed April 26, 1967 Sheet of 2 F! G E:-

ATTORNEY United States Patent 3,418,888 HYDRAULIC ACTUATOR WITH INTERNAL DASHPOT Jacques H. Mercier, 1199 Park Ave., New York, N.Y. 10028 Filed Apr. 26, 1967, Ser. No. 633,975 Claims priority, application France, Apr. 27, 1966,

2 Claims. Cl. 91-396) ABSTRACT OF THE DISCLOSURE The present invention relates to a hydraulic actuator including a cylinder and piston with damping at the end of a stroke, and more particularly to an actuator in which the cylinder has a fluid port adjacent one end thereof and in which the piston is movable toward such end and defines a chamber with respect thereto in communication with the said fluid port, with dashport means to restrict such communication when the piston is moved adjacent said end of the cylinder.

In the known devices of this type, the dashpot means are generally provided in the end of the cylinder.

It is among the objects of the present invention to provide an actuator in which the dashpot means is independent of the end of the cylinder so that plugs of the same type which are used to close the end of the cylinder can be adapted to cylinders of dilferent diameters in view of simplifying the manufacture of the actuator.

Summary of the invention According to the invention, the dashpot means comprises a separate member adapted to be placed inside the cylinder against one end of the latter, the member having an axial bore into which a terminal projection of the piston is adapted to move, communication means with a large cross section being provided between the cylinder chamber and the fluid port provided in the cylinder adjacent said end thereof, prior to movement of the terminal projection into the bore of said member and communication means with a small cross section when said projection has entered said bore.

According to a feature of the invention, means are provided substantially to suspend the dashpot eflect as soon as the piston moves in the opposite direction even while the projection is still in the bore of the dashpot member in order to avoid any unnecessary slowdown in operation.

Brief description of the drawings In the accompanying drawings in which are shown one or more of various possible embodiments of the several features of the invention:

FIG. 1 is a general schematic view of an actuator to which the invention is applied;

FIG. 2 is a view on a larger scale of one end of the actuator, in a longitudinal section along the line IIII of FIG. 3,

FIG. 3 is a corresponding view in cross section along the line 1IIIII of FIG. 2;

FIG. 4 shows a one-way valve of the device in a section along the line IVIV of FIG. 3;

FIG. 5 is a perspective view of a split bushing retainer for the dashpot member;

FIG. 6 is a perspective exploded view illustrating the mounting of the dashpot member, and

FIG. 7 is a fragmentary view, similar to FIG. 2, but concerning a variant of the retainer for the dashpot member.

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Referring now to the drawings, in FIGS. 1 to 6 a cylinder 10 is provided which has a side wall 11 closed at one end by a plug 12 which has a longitudinally extending ear 13 with an opening 14 to permit pivotal mounting of the cylinder 10 about an axis through said opening 14.

The plug 12 has a reduced diameter portion 15 which is centered in the end of the cylinder 10 and which is fixed to the latter by a welded seam at 16.

A threaded sleeve 17 is secured as by welding to the side Wall 11 of the cylinder 10 adjacent end plug 12 and is designed to receive a pipe line (not shown). The side wall 11 of the cylinder 10 has an opening 18 defining a fluid port aligned with the vbore of sleeve 17.

A piston 19 is slidingly mounted in the cylinder 10 and has encompassing seal rings 20. A piston rod 21 secured to piston 19 extends through the opposite end 10' of the cylinder.

The portion of the cylinder 10 between plug 12 and piston 19 defines a chamber 22 in communication with the sleeve 17, dashpot means being provided to restrict such communication when the piston 19 is moved to the immediate proximity of the plug 12.

According to the invention, such dashpot means comprises a member 23 shown in a perspective view in FIG. 6, which is separate from the cylinder 10 and which is adapted to be placed inside the latter against the plug 12.

The member 23 is in the form of a cylindrical plug having one end wall 25 against plug 12 and the other end Wall 24 forming a wall of chamber 22. The outer surface 26 of the plug is of diameter such that it can be fit without much play in the bore of the cylinder 10. The outer surface 26 has an annular groove adjacent end wall 24 in which a seal ring 27 is positioned.

The member 23 has an internal bore having two portions 28, 29 with different diameters, the portion 28 adjacent the end wall 24 having a smaller diameter than the portion 29 adjacent end wall 25. The bore portions 28, 29 are designed to receive at the end of the inner stroke of the piston 19, an axial terminal projection 30 of the latter, which is engaged with minimum clearance in the smaller diameter portion 28, while an inter-communication space 31 is provided by the larger diameter portion 29.

The member 23 has a radial bore 32 with a large cross section which extends between the internal bore of member 23 and its periphery 26 and which is of enlarged diameter as at 33 at its outer end, preferably of the same diameter as the opening 18 in the wall 11. A resilient bushing 34 split as at 35 is forced into the opening 18 and enlarged diameter portion 33 resiliently to lock member 23 in the cylinder 10.

The bore of bushing 34 defines a fluid passage 36 of the same diameter as the bore 32.

The member 23 has a longitudinal passageway 38 extending from end wall 24 into a radial internally threaded bore 39 which is of reduced diameter at its inner end as at 37 leading into bore portion 29. A screw 40 tapered at its inner end 40' is screwed into bore 39 to permit regulation as at 41 of the flow through bore portion 37. A port 42 is provided in the side wall 11 of the cylinder 10 aligned with bore 39 to permit adjustment of screw 40, the port 42 being closed by plug 43.

In addition, the member 23 has a longitudinal passageway 44 circumferentially spaced from passageway 38, extending from the end wall 24 into a radial bore 46 which is of reduced diameter at its inner end 44' leading into bore portion 29. A one-wayball valve 45 in bore 46 permits the circulation of fluid in the direction 29, 44 and prevents the circulation of fluid in the opposite direction.

A port 47 is provided in the side wall 11 aligned with the bore 46 and receives a plug 48 forming a drain plug.

It is to be noted that the end closure plug 12 provided with the car 13 is independent of the dashpost member 23. Consequently, identical plugs 12 with cars 13 can be provided, and it is merely necessary to form the portion 15 with a desired diameter as by a cut-oil lathe, to give it a diameter corresponding to each cylinder. The result is a simplification and considerable economy in manufacture.

In operation, when the piston 19 is displaced from right to left, as long as the projection 30 had not approached the member 23, fluid will flow from chamber 22 through bores 28, 29 and 32, port 18 and through sleeve 17. When the projection 30 penetrates into the bore portion 28, fluid can no longer leave the chamber 22 except through the passage 38, 37 with the constriction 41, and since the valve 45 (FIG. 4) is closed, there is no flow through the passage 44. Thus, a dashpot eflect is provided which cushions the arrival of the piston 19 at the end of the stroke.

When the piston 19 starts to move from left to right, the oil can pass from the sleeve 17 to the chamber 22, through the valve 45, with a suflicient flow which will avoid any slowdown in the starting movement.

In the embodiment shown in FIG. 7, the arrangement is similar to that described above with reference to FIGS. 1 to 6, but the retainer for the member 23 is not a bushing but a hollow plug 50 which is screwed into the sleeve 17 and provides a passage 51 for the fluid.

The screw 50 penetrates into the member 23 with a conical engagement at 52, 53 which tends to force the member 23 against the plug 12. To this end the conical bearing surface 52 on the plug 50 has a smaller diameter than the corresponding conical bearing surface 53 of the member 23.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is.

1. A hydraulic deevice comprising a cylinder having opposed closed ends, a piston slidably mounted in said cylinder and defining a chamber with respect to one of said closed ends, a piston rod secured to said piston and extending axially of said cylinder through the other end thereof, said cylinder having a fluid port in the wall thereof adjacent said first end, a plug positioned in said cylinder adjacent the first end of the latter, said plug having an axial bore, said bore having longitudinally aligned small diameter and large diameter ortions, the

large diameter portion of said bore being adjacent the closed end of said cylinder, said plug having a radial passageway aligned at its outer end with said fluid port and in communication therewith and aligned at its inner end with the enlarged diameter portion of said bore, said plug having an additional radial passageway having its inner end in communication with the enlarged diameter portion of said bore, and having an additional passageway in communication at one end with said last named radial passageway and at its other end with said chamber, said additional passageway and said associated radial passageway being of smaller diameter than the radial passageway in communication with said fluid port, said piston having an axial extension on the side thereof adjacent said chamber, said extension being of diameter substantially equal to the small diameter portion of said bore in said plug whereby when said piston has moved adjacent said first end of said cylinder and said extension has moved into said small diameter portion of said bore, communication between said chamber and said fluid port will be solely through said additional passageway and associated radial passageway to provide a dashpot action, said radial passageway in said plug aligned with said fluid port is of enlarged diameter at its outer end, said fluid port in said cylinder is substantially the same diameter as said enlarged diameter portion of the associated radial passageway and a substantially tubular locking member is positioned in said fluid port and said enlarged diameter portion of said associated radial pas sageway to prevent movement of said plug in said cylinder.

2. The combination set forth in claim 1 in which said locking member is a split sleeve.

References Cited UNITED STATES PATENTS Re. 24,532 9/1958 Hallady et al. 91-26 3,303,746 2/1967 Schmueger 9126 FOREIGN PATENTS 825,812 12/1937 France. 562,073 6/ 1944- Great Britain.

PAUL E. MASLOUSKY, Primary Examiner.

U.S. Cl. X.R. 

